Nancy Writebol, left, is the second U.S. citizen working in Liberia that has tested positive for the Ebola virus. She is seen with her husband David.

Nancy Writebol, American With Ebola, to Arrive in U.S. on Tuesday

Nancy Writebol, one of the two Americans who were infected with Ebola in Liberia, is expected to arrive in the United States at around midday on Tuesday to be treated at an Atlanta hospital, sources told NBC News.

Bruce Johnson, the president of SIM USA, an aid organization that Writebol works with, told MSNBC that she was “up and walking” and that she was getting stronger. She felt well enough to eat her favorite Liberian dish, potato soup, he said. He said that Writebol had received two doses of an experimental Ebola serum.

The other American, Dr. Kent Brantly, is already at the hospital and said to be improving. The two were working with a missionary organization, Samaritan’s Purse, when they contracted Ebola. More than 1,300 people have been sickened in the worst known outbreak of the virus.